A new specimen of Parahughmilleria sp. is described from the Early Devonian Dundee Formation (Arbuthnott Group, Lochkovian) from the Tillywhandland Quarry (Forfar) in the Midland Valley of Scotland. The diversity of eurypterids from the Midland Valley assemblage is reinterpreted to comprise six species (although systematic revisions await the discovery of more material and formal revisions of each genus): Pterygotus anglicus Agassiz, 1844 (including Pterygotus minor Woodward, 1864, here interpreted as a juvenile), Tarsopterella scotica Woodward, 1872 (including Erieopterus brewsteri Woodward, 1864, here interpreted as a juvenile), Stylonurus powriensis Page, 1856 (including Stylonurus? ensiformis Woodward, 1864, here interpreted as a partial piece (telson) of a large individual), Pagea sturrocki Waterston, 1962, Nanahughmilleria pygmaea Salter, 1859 and Parahughmilleria sp. Functional evidence and their general occurence favours a benthonic mode of life for the stylonurids, which inhabited fluvial systems surrounding ‘Lake Forfar’, whereas the pterygoids and hughmillerids inhabited the lacustrine facies.